Endoscopes are commonly used for observing, studying and/or treating internal body tissues and structure. An endoscope may include, for example, an eyepiece assembly and a distal section. The eyepiece assembly may include, for example, an objective lens, and the distal section is sized to be passed into the internal body region that is to be viewed or treated.
After each usage, it is necessary to thoroughly sterilize at least the distal section of the endoscope, and this is time consuming. It has been proposed in Heine et al U.S. Pat. No. 4,306,546 to disconnectably couple the distal section of an endoscope to a head so that the distal section can be discarded, and the head can be reused. However, this endoscope does not provide for angularly orienting the distal section relative to the head, and therefore, cannot be used if such orientation is necessary.
To enable an endoscope to be used for viewing, it is necessary to conduct light from the eyepiece assembly to the distal section and to conduct an image through the distal section to the eyepiece assembly for viewing by the physician. To enable the image to be conducted, the distal section may comprise a rigid body and lenses or a rigid image-conducting rod within the body. However, the lenses and/or the rigid image-conducting rod tend to break if the body of the distal section is distorted. Alternatively, coherently aligned optical fibers may be used for image transmission. Although the optical fibers are flexible and not likely to break, it is quite costly to obtain the necessary coherent alignment of the optical fibers so that they will transmit an image. Flexible endoscopes are known, but their flexibility limits their maneuverability within the patient.
Focusing of the optics of the endoscope can be accomplished, for example, as shown in Olinger et al U.S. Pat. No. 3,941,121 by rotating a threaded member of the eyepiece assembly in and out. However, the repeated axial advance and retraction of the threaded focusing member increases the likelihood of migration of dirt and other contaminants into the interior of the endoscope. This is unsuitable for an instrument which is to be sterile.
A common technique for introducing an endoscope is to insert a sleeve containing a pointed rod through a cut in the skin and then advancing the pointed rod to form a portion of the desired passage. The pointed rod is then removed, and a blunt rod is inserted through the sleeve to complete formation of the passage. After the blunt rod is removed, the endoscope can be inserted through the sleeve. This technique requires the use of a multiplicity of components, each of which must be resterilized prior to subsequent use. In addition, this technique may cause trauma. It is also known to introduce a probe or catheter into the vascular system by inserting a relatively large diameter needle into the vascular system and then inserting the probe or catheter through the needle. Although this technique has not, to our knowledge, been applied to endoscopes, there is no adequate way to minimize injury due to the needle following insertion.